Flashlamps

ABSTRACT

A flashlamp comprises a transparent bulb with its internal volume 2.0 cc. or less, a luminescent material, combustionassisting gas having 100 to 130 percent by weight of the chemical equivalent necessary for combustion of said material, and first and second main lead-in wires supporting a filament. Said first wire has a diameter of 0.2 to 0.6 mm. The lamp further includes an auxiliary lead-in wire disposed in parallel with the first wire and spaced therefrom by 75 percent or less of its diameter as of the diameter of said first wire.

i United States Patent [72] Inventors Kenji Ohlnae Yokohama-ski; Namio mu, Odawara-shi; Osamu Nomura, Yokohama-shi. all of. Japan [2|] Appl. No. 864.860

[22] Filed Oct. 8. I969 Patented Aug. 10, 197i 73] Assignee Tokyo Shibaun Electric Co., Ltd.

Kawasaki-slit, Japan [32] Priority Oct. 9, 1968, Aug. 25. I969 3 3 Japan l 43/73347 and 44/80125 [54] FLASHLAMPS 8 Claims, 7 Drawing Figs.

[51] lnt.Cl. F2lk5/02 Field olSearch a 431/93,

[56] References Cited UNITED STATES PATENTS 1 3,045,460 7/l962 Brouse et al 43 l/95 3.471880 10/1969 Wick 431/95 Primary Examiner- Edward J. Michael Attorney- Flynn & Frishauf ABSTRACT: A flashlamp comprises a transparent bulb with its internal volume 2.0 cc. or less, a luminescent material, combustion-assisting gas having to percent by weight of the chemical equivalent necessary for combustion of said material, and first and second main lead-in wires supporting a filament. Said first wire has a diameter of 0.2 to 0.6 mm. The lamp further'includes an auxiliary lead-in wire disposed in parallel with the first wire and spaced therefrom by 75 percent or less of its diameter as of the diameter of said first wire.

PATENTEUIIIIBIOIIII' 3.598.511

SHEET 2 OF 3 FIG. 3

FUSING SHORT-CIRCUIT PERCENTAGE a o 011 012613 o.'4 o.'s 0'6 61 6? 0'9 1'5" I SPACING g(mm) BETWEEN MAIN AND AUXILIARY I LEAD-IN WIRES YPATENTED mm 0.9-

sum 3 OF 3 FIG. 6

FLASHLAMPS This invention relates to a flashlamp adapted to give sequential flashes.

In recent years, various flashing devices of a sequential flash type have been developed in which a plurality of flashlamps mounted in the flash shoe are energized in sequence. The flashlamp of this nature comprises a transparent glass bulb, a luminescent material and a combustion-assisting gas hermetically sealed in said bulb, a filament cased in said bulb, and a pair of lead-in wires supporting the filament and supplying an electric current thereto.

The sequential flashing operation may be carried out, for example, by mechanically switching the input terminals of a series of flash lamps or by electrically switching the contacts thereof, both outside the flashlamps. These methods, however, do not always provide reliable operation. In particular, the former is not only required to have a complicated construction but is also subject to insufflcient contacts which will result in nonignition of the lamps.

A device used in the latter method is expensive and less durable. Further it is not satisfactory for positive flash photography because of a possible failure in ignition resulting from for example, insufficient contacts.

In addition to the mechanical and electrical switching of contacts, an automatic flashing device is known in which thermal switches are provided for a plurality of parallel connected flash lamps which are automatically sequentially closed.

Namely, the lead-in wires of two adjacent flashlamps are opposed to each other outside the flashlamps and a chemical substance is placed between the opposing lead-in wires.

The chemical substance is normally an insulator, but serves a good electrical conductor by reaction at elevated temperatures at the time of flashing, or is capable of thermal expansion or contraction at elevated temperatures so as to short circuit the lead-in wires, when heated at the time offlashing.

These thermal switches, however, have certain disadvantages in that it is difficult to provide switching material capable of being converted from an insulator to a sufficiently good conductor when heated at the time of flashing or capable of being thermally expanded or contracted; and the switching material tends not to properly react since the thermal conductivity varies depending upon the thickness of a synthetic resin layer or the like coated on the glass bulb for avoiding the collapse of the bulb, with the result that an amount of the insulator is left between the lead-in wires or the material remains unexpanded due to insufficient heating. It has thus been difficult to employ such thermally reacting material as a thermal switch element.

Further, the provision of thermal switches about the flash lamps is not suitable for manufacture on a mass production basis because of additional material and processing required.

The flashlamp of the present invention comprises a transparent bulb having an internal volume of 2.0 cc. or less, a luminescent material and a combustion-assisting gas both sealed in the bulb, said combustion-assisting gas having 100 to 130 percent by weight of a chemical equivalent necessary for the combustion of the material, a pair of main lead-in wires 0.2 to 0.6 mm. in diameter having one end extending into the interior of said bulb, a filament bridged between the lead-in wires, an auxiliary lead-in wire of almost the same diameter as that of the main lead-in wires and extending into the interior of the bulb along one of said main lead-in wires with a spacing equal to 75 percent or less of the diameter of the main lead-in wire.

In operation a plurality of flashlamps are connected in a predetermined manner and operated sequentially without relying upon mechanical or electrical switches exterior to the bulb.

This invention can be more fully understood from the following detailed description when taken in connection with reference to the accompanying drawings, in which:

FIG. 1 shows a cross sectional view of a flashlamp embodying this invention;

FIG. 2 is an enlarged elevational view illustrating lead-in wires of the flashlamp shown in FIG. 1;

FIG. 3 is a curve showing the relationship between the short circuiting and spacing between main and auxiliary lead-in wires in accordance with this invention;

FIG.'4 is a cross-sectional view of the flashlamp further embodying this invention;

FIG. 5 is a circuit diagram for operating the flashlamp shown in FIG. 4;

FIG. 6 is a perspective view of a flash shoe loaded with flashlamps of FIG. 4 according to the circuit arrangement of FIG. 5 in connection with the body of a camera; and

FIG. 7 is a cross-sectional view of a modification of the flash bulb ofthe invention.

The arrangement of the flashlamp and restrictive factors of each element of the invention will be first described in connection with FIGS. 1 to 3.

The flashlamp 14 comprises a transparent glass bulb l0 having an internal volume of 2.0 cc. or less, a luminescent material sealed in the bulb 10, a combustion-assisting gas sealed in the tube in an amount equal to I00 to 130 percent by weight of a chemical equivalent necessary for the combustion of the luminescent material, an electrode assembly 12 disposed within the bulb at one end thereof, and a gas exhaust portion 13 sealing the tube at the other end thereof. The electrode assembly 12 has a pair of main lead-in wires 15 and 16 and an auxiliary lead-in wire 17. The main lead-in wires 15 and 16, 0.2 to 0.6 mm. in diameter, may be made of a metal usually employed in the art for this purpose, such as an iron-nickel alloy or nickel. The auxiliary lead-in wire 17 having a similar diameter is disposed in parallel to one of the main lead-in wires, say, the lead-in wire 16, with a rated spacing equal to 75 percent or less of the diameter of the main wire. These lead-in wires 15, 16 and 17 are fusion welded to a glass bead 18 at predetermined positions. An ordinary ignition filament is bridged between the main lead-in wires 15 and 16.

The specific internal volume 2.0 cc. or less of the bulb is critical. If the internal volume of the bulb exceeds said specific value, the luminescent material, when sealed in the minimum amount required for ordinary flashing, will be unevenly distributed-thick in the upper part of the bulb-and insufficient heat will be produced to melt the main and auxiliary wires 16 and 17. It has been found that satisfactory melting of the leadin wires is attained when the amount ofthe luminescent material per unit volume of the bulb is 10 mgQ/cc. or more. This will of course vary depending on the luminescent materia] used, but this applies, in this case, to an ordinary luminescent material such as aluminum or zirconium wire or foil used in the art.

An explanation is now given to the rated amount of the combustion-assisting gas which is to l30 percent by weight of the chemical equivalent required for combustion of the luminescent material. Since the heat generated only by combustion of the sealed luminescent material will not be enough to melt and thus short circuit the first main wire 16 and the auxiliary wire 17, combustion of a part of the wire is additionally needed to completely melt and short circuit both wires 16 and 17. Experiments have shown that 100 percent or more by weight of the chemical equivalent of the luminescent material is required to burn a part of the wire as welL'When exceeding the above amount, more heat will be generated by combustion of the luminescent material. When exceeding the maximum amount (130 percent by weight), the ordinary glass bulb is in danger of explosion or destruction.

Specific numerical values regarding the diameters of the main lead-in wires 15 and 16 and the spacing between the first main wire 16 and the auxiliary wire 17 have been obtained on the basis of an experiment described below. The rated internal volume of the bulb is 1.2 cc. The rated amount of the combustion-assisting gas is to H5 percent by weight of the chemical equivalent required for combustion of the sealed luminescent material. The main and auxiliary lead-in Dumet wires with their diameters of 0.4 mm. are employed. The rated spacing g (FIG. 2) between the first main and auxiliary lead-in wires is divided into 14 groups within the range 0.0l0.85 mm. Twenty flashlamps are fabricated in each group. The percentage of short circuit by melting together is obtained in each group. The results are shown in FIG. 3. In this figure the X axis denotes the spacing g (mm.) and the Y axis the fusing short circuit percentage. This clearly shows that the spacing g must be 0.3 mm. or less to obtain a 100 percent by weight short circuiting by melting together.

Similar experiments were conducted by varying the internal volume of the bulb, the amount of the gas, and the diameters of the lead-in wires. It has been found that the same results can be obtained by rating the internal volume of the bulb to 2.0 to 0.6 cc., the amount of the gas to 100 to I30 percent by weight of the chemical equivalent required for combustion of the luminescent material, the diameter of each lead-in wire to 0.2 to 0.6 mm. and the spacing g to 75 percent or less of the diameter of each main lead-in wire. So far as short circuiting by fusing is concerned, it is preferred that the spacing g is as small as possible within the limit of 75 percent or less of the diameter of the main wire. To secure electrical insulation between the main and auxiliary wires prior to the flashing operation, however, the spacing g preferably is determined within the limits 15 to 75 percent of the diameter of either main wire. It has been experimentally confirmed that the optimum percentage of short circuiting by melting together can be obtained if the diameter of the auxiliary wire is selected to be almost the same, more exactly with -l0 percent tolerances as that of either main wire. It has also been found that, under these conditions, accurate short circuiting by fusing can be obtained by melting together the main and auxiliary wires into one and accurately retaining the melted metals flowing into the main and auxiliary wires due to surface tension of the melted metals, thereby burying the space therebetween.

Referring now to FIG 4 showing a modification of the flash lamp 24 of the present invention, a luminescent material 2| and a combustion-assisting gas are hermetically sealed in a transparent glass bulb having an internal volume of L2 cc. The luminescent material is a thin zirconium wire ll of 36.0 mg. and the combustion-assisting gas is 31.68 mg. of oxygen. ln this case, argon, for example, may be added to delay combustion of the gas. The first and second main lead-in wires 25 and 26 are fusion welded on the glass bead 28 with a predetermined spacing. These wires are made of Dumet wire with its diameter 0.4 mm. The auxiliary lead-in wire 27 is disposed in parallel to the first main lead-in wire 26 and has the same material and diameter as those of the main wire. The spacing between the first main wire 26 and the auxiliary wire 27 is 0.3 mm. The ordinary ignition filament 29 is bridged between the two main lead-in wires 25 and 26. An ignition agent is applied on the filament and main lead-in wires 25 and 26 and, ifnecessary, on the auxiliary wire 27.

In practical use, a number of flashlamps prepared in accordance with the present invention may be constructed and arranged as follows.

As shown in FlG. 5, the first main lead-in wire 26 of the first flashlamp 24 is connected to one terminal ofthe power source E through a normally open contact S which interlocks with a shutter, The second main lead-in wire 25 of this flash lamp 24 is connected to the other terminal of the source E through a resistor R. A capacitor C is connected in parallel to the lower source E between the power source E and the second main lead-in wire. The auxiliary wire 27 of the first flashlamp 24, and the firsf main wire 26 of a second flashlamp 24, and the first main wire 26 of a second flashlamp 24 are electrically connected with each other. The other flash bulbs are respectively connected together in the same way as above.

The flashlamps 24 thus arranged are cased in a flash shoe 40, as shown in FIG. 6. This flash shoe 40 consists ofa base 41 and a flashlamp supporting member 42 in which four recesses 43 are formed. Aluminum-vapor-deposited reflectors 44 are mounted on the inner surfaces of the recesses 43, respectively. The base '41 is mounted on the body of a camera 45 which contains the power source E, resistor R, capacitor C and switch S. The switch S is connected to the shutter button 46 so as to be turned on by pressing down the shutter button 46.

In this manner, the first flashlamp mounted in the flash shoe will be lit by depressing the shutter. The main and auxiliary lead-in wires will be melted together by the heat generated during the flash time, thus short circuiting the first main and auxiliary lead-in wires. As a result, the first main wire of the second flashlamp will be connected to the power source E through said contact S. Accordingly, if the shutter is pressed again, the second flashlamp, which is now set for action, will be flashed.

Referring now to FIG. 7 showing a further modification of the present invention, the same references as those in the previous embodiment are used to designate like portions and a detailed description thereof is omitted. The transparent glass bulb with an internal volume of 2.0 cc. is employed. Eighty milligrams of fine aluminum wire as a luminescent material 21 and approximately 81 mg. of oxygen as a combustion-assisting gas are sealed hermetically in the bulb 20. The first and second main lead-in wires 25 and 26 are made of an ironnickel alloy. Their equal diameters are 0.6 mm. The auxiliary lead-in wire 27 is disposed in parallel in its upper part to the first main lead-in wire 26 and is made of the same material and has the same diameter as the first main lead-in wire 26. The spacing between these two wires preferably is 0.4 mm, An antioxidant (not shown) is applied on the surfaces of the first main lead-in wire 26 and the auxiliary lead-in wire. A recess 40 is formed in the glass bead at a portion including the first main lead-in wire 26 and the auxiliary lead-in wire 27. When the lead-in wires 26 and 27 are melted due to the heat generated by the combustion of the luminescent material, the melted metals will be collected in this recess 40 so as to short circuit these lead-in wires. Reference numerals 23 and 29 designate the sealed tube and the ignition filament, respectively.

What we claim is:

- l. A flashlamp for enabling successive flashing ofa plurality oflamps, comprising: i

a transparent bulb having a maximum volume of 2.0 cc.;

a luminescent material sealed in said bulb;

a combustion-assisting gas having to l30 percent by weight of the chemical equivalent necessary for combustion of said luminescent material and hermetically sealed in said bulb;

first and second main lead-in wires inserted through said bulb, said first lead-in wire having a diameter of0.2 to 0.6

a filament bridged between the main lead-in wires within the bulb; and

an auxiliary lead-in wire having substantially the same diameter as that of said first main lead-in wire, the upper part thereof being disposed in parallel with said first main lead-in wire and being spaced from said first main lead-in wire by a maximum of 75 percent of the diameter of said first main lead'in wire.

2. A flashlamp according to claim I wherein an ignition agent is applied on the contacts ofsaid main lead-in wires with said filament.

3. A flashlamp according to claim I wherein an antioxidant is applied on the surfaces of said main and auxiliary lead-in wires.

4. A flashlamp according to claim I wherein the luminescent material is a fine wire made of at least one material selected from the group consisting of zirconium and aluminum.

5. A flash lamp according to claim 1 wherein said main and auxiliary lead-in wires are fixed in predetermined positions by means of a glass bead.

6. A flashlamp according to claim 5 wherein the glass bead is formed with a recess on its upper surface in a portion through which the auxiliary lead-in wire and the first main lead'in wire are inserted.

7 A flashlamp according to claim 5 wherein said glass bead 8. A flashlamp according to claim 7 wherein said glass bead is located within the lower end of said bulb adjacent a lower is secured to said lower surface ofsaid bulb. surface ofsaid bulb. 

2. A flashlamp according to claim 1 wherein an ignition agent is applied on the contacts of said main lead-in wires with said filament.
 3. A flashlamp according to claim 1 wherein an antioxidant is applied on the surfaces of said main and auxiliary lead-in wires.
 4. A flashlamp according to claim 1 wherein the luminescent material is a fine wire made of at least one material selected from the group consisting of zirconium and aluminum.
 5. A flash lamp according to claim 1 wherein said main and auxiliary lead-in wires are fixed in predetermined positions by means of a glass bead.
 6. A flashlamp according to claim 5 wherein the glass bead is formed with a recess on its upper surface in a portion through which the auxiliary lead-in wire and the first main lead-in wire are inserted.
 7. A flashlamp according to claim 5 wherein said glass bead is located within the lower end of said bulb adjacent a lower surface of said bulb.
 8. A flashlamp according to claim 7 wherein said glass bead is secured to said lower surface of said bulb. 